1. Field of the Invention
The present invention relates to a pressure switch capable of sending a detection signal to an external device when a measured pressure of a pressurized fluid measured by a pressure sensor coincides with a predetermined set pressure.
2. Description of the Related Art
A known vacuum carrying device put a suction cup on a workpiece, creates a partial vacuum in the suction cup to hold the workpiece by the vacuum on the suction cup and carries the workpiece held by the suction cup to a predetermined position. A pressure switch is used to confirm the creation of a predetermined vacuum in the suction cup and to ensure that the workpiece is securely attracted to the suction cup by suction.
The pressure switch is provided with a pressure sensor for measuring a vacuum created in the suction cup. The pressure switch decides that the suction cup has firmly held the workpiece upon the coincidence of a measured pressure measured by the pressure sensor with a predetermined pressure and sends a complete attraction detection signal indicating the complete attraction of the workpiece by the suction cup to, for example, an external controller.
A pressure switch of this kind disclosed in, for example, JP-A 2000-173377 is provided with a display unit for displaying a set pressure.
When this known pressure switch is incorporated into a work carrying apparatus or the like, the operator is supposed to read the set pressure displayed by the display unit from a predetermined direction, namely, a reading direction, and to operate operating buttons or the like from a predetermined direction, namely, an operating direction. Even if the environment in which the pressure switch is installed does not allow the operator to read the set pressure and to operate the operating buttons from the fixed reading and the fixed operating direction, the set pressure cannot be read from a direction opposite the reading direction and the operating buttons cannot be operated from a direction opposite the operating direction.
The known pressure switch needs to be connected to the suction cup by a line for carrying a fluid of a negative pressure and needs to be installed fixedly at a predetermined position. Consequently, the set pressure displayed by the display unit can be read only from a fixed reading direction and the buttons need to be arranged in a fixed direction.
Therefore, if the arrangement of the pressure switch is changed and the operator is obliged to look at the set pressure from a direction opposite the predetermined direction and the operating buttons are arranged inevitably in a direction opposite the predetermined direction, it is possible that the operator fails in reading the set pressure correctly and the operator is liable to fail in correctly operating the operating buttons. Such problems arise also when the pressure switch is installed in an inverted position.